The invention relates to wind turbines with rotor blade adjustment (also called pitch control or pitch adjustment). Such wind turbines have a rotor blade bearing for their adjustable rotor blade—said bearing also being called a slewing ring bearing. The invention relates in particular to the servicing of such wind turbines.
Wind turbines typically have a rotor with a hub on which a plurality of rotor blades are mounted in most cases. In order to adjust the pitch angle of a respective rotor blade, a blade adjustment means is usually provided. This may comprise a slewing ring whose movable part is connected via a rotary bearing to the hub and is thus rotatable about a longitudinal axis of the blade with respect to the hub. The respective rotor blade is fastened to the movable part and is thus likewise rotatable about its longitudinal axis and adjustable in pitch with respect to the hub.
Such slewing rings of the kind used in wind turbines generally form a unit with the rotary bearing and as a unit generally have an inner and an outer ring, as well as rolling elements, spacers or a cage. The part which is adjusted is the freely rotatable part of the unit, which is referred to in the following as the movable slewing bearing part, and which is joined to the rotor blade. The counterpart is rigidly joined to the hub. Adjustment is normally carried out with the aid of a gearbox-motor combination via toothing on the slewing ring bearing.
In wind turbines with electric blade control, the toothing of the rotor blade bearing, i.e., the toothing of the slewing ring bearing in the range between about 0° and 5° blade pitch angle (blade position), may be subject to increased wear and tear. This is due to blade adjustment in the upper load range of the wind turbine.
In wind turbines with blade pitch control, the used portion of the toothing generally amounts to 90°. The blades are moved within the range between 0° and 90°. The range between 0° and 5° is viewed as the working range. Wear and tear is at its maximum in this range. Within the working range, the lubricant applied is displaced by permanent movement of the drive, thus resulting in greater abrasion of the respective locale. When the wear limit is reached, it is necessary to turn the position of the rotor blade bearing with respect to the rotor blade, so that unworn teeth in the toothing on the slewing ring bearing engage with the drive.
Two methods are currently used for turning the rotor blade bearing. In the first method, the rotor of the wind turbine is dismantled. The blades are dismantled singly using two mobile cranes, the movable slewing bearing part is moved and the rotor blade is remounted. In the second method, the rotor blade is dismantled, while the rotor remains mounted, using two cranes or one crane. In the latter case, a frame is used which keeps the blade in balance. The movable slewing bearing part is moved and the rotor blade is then remounted. In both methods, the movable slewing bearing part is moved into the region which was unused until that time.
An alternative, preferably simpler procedure for servicing wind turbines is desirable.